Suggest Remedy For Knee Pain Due To Injury

Hi

I injured my knee in rugby last week. When I injured it I heard a loud popping sound, my knee is swollen and very pain full when I walk, when I climb stairs it keeps on giving in and I find it difficult and pain full to bend it. I did some research and it seems that I have torn an “ACL” ligament. Do I need to go for surgery or will the pain go away if I just leave it???